1. Field of the Invention
The present invention relates to a printing medium transferring mechanism for making a print on a printing medium which cannot be bent such as a thick printing medium, a printing medium not wished to be bent and a CD-R.
2. Description of the Related Art
In a printing apparatus such as an ink jet printing apparatus, while moving and scanning a printing head for applying a printing agent relative to a movement of a printing medium, an image is formed on the printing medium. In this event, in a case of a relatively flexible printing medium such as plain paper, it is common that printing medium loaded on a tilted paper feed tray are fed one by one by a paper feeding roller, and that a transferring direction is changed while slightly curving the printing medium along the paper feeding roller. Thereafter, a print is made on the printing medium, and the medium is transferred. However, in a case of printing on a thick printing medium, a printing medium not wished to be bent and a CD-R, it is necessary to perform all transfer within the same plane since the printing medium cannot be bent. Such a transferring operation within the same plane will be hereinafter called a flat-pass in the present specification.
There has been already proposed and implemented a configuration for realizing a normal transferring path and a flat-pass while using the same conveying roller in the printing apparatus (see, for example, Japanese Patent Application Laid-open Nos. 2002-192782, 2003-211778 and 2004-042391).
Japanese Patent Application Laid-open No. 2002-192782 discloses a configuration for installing a printing medium by allowing a user to separate a pair of conveying rollers for transferring the printing medium from each other, or to press the pair to be in contact with each other, while holding the medium from above and below. Specifically, in a case of printing by use of a flat-pass, the user first separates the pair of conveying rollers from each other, inserts a printing medium, such as cardboard, from a horizontal direction, and further causes the pair of conveying rollers to be in contact with each other by pressure. Thus, the printing medium is installed. That is, because a paper feeding step is performed in a horizontal position by the user, the flat-pass can be realized in a state where the printing medium is not curved due to a paper feeding operation.
Japanese Patent Application Laid-open No. 2003-211778 discloses a configuration for automatically separating the pair of conveying rollers from each other, and for automatically pressing the pair to be in contact with each other, by utilizing a driving source, such as a motor, and cams.
Moreover, Japanese Patent Application Laid-open No. 2004-042391 discloses a configuration in which a space is provided between a pair of conveying rollers by attaching a detachable guide member to the printing apparatus. Two pairs of conveying rollers are normally prepared respectively on upstream and downstream sides of a region where printing is made by the printing head. However, according to the foregoing document, the pair of conveying rollers, which is separated by inserting the guide member, is limited to the pair of conveying rollers on the downstream side relative to a printing medium transferring direction. Thus, the configuration is designed to also cause the pair of conveying rollers on the upstream side to easily nip the printing medium by attaching a different member thinner than the printing medium to a tip of the printing medium.
However, the methods described in the patent documents described above have several problems.
For example, as described in Japanese Patent Application Laid-open No. 2002-192782, the configuration in which the user manually separates and pressure-contacts the conveying rollers from each other, troubles the user, and causes a risk of malfunction. Moreover, as described in Japanese Patent Application Laid-open No. 2003-211778, even the configuration, in which separation of the pair of rollers from each other and pressing the pair to be in contact with each other are automatically performed, requires the user to insert the printing medium up to a position where the medium is held by the conveying rollers, and to check if the medium is held or not. Thus, it is still troublesome for the user to perform such an operation.
In the configuration described in Japanese Patent Application Laid-open No. 2004-042391, the user can realize a flat-pass only by attaching the guide member. However, as described above, since the different thin member has to be attached to the tip of the printing medium, new problems are brought about, such as that a limitation is placed on the printing medium which can be used, and that another operation for attaching the different thin member is required.
Furthermore, in order to realize a secure flat-pass, it is desired that the printing medium is reliably held by the pair of conveying rollers on the upstream side. For example, in a case of a configuration in which the printing medium is inserted from the downstream side, a limitation is placed on a size of the printing medium depending on a printing apparatus. This is because there is concern for a case where, if the printing medium is not one having a predetermined length or more, the printing medium cannot be inserted up to a depth where the medium is held by the pair of conveying rollers on the upstream side. In order to improve workability of the user while minimizing an installation area of the printing apparatus as much as possible, a configuration, in which the printing medium is inserted from a front face (i.e., the downstream side), is regarded as appropriate. Hence, in the printing apparatus having the configuration, a limitation is inevitably placed on the size of the printing medium which enables flat-pass printing.